KVM: PPC: Book3S HV: Don't take kvm->lock around kvm_for_each_vcpu

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Currently the HV KVM code takes the kvm->lock around calls to
kvm_for_each_vcpu() and kvm_get_vcpu_by_id() (which can call
kvm_for_each_vcpu() internally).  However, that leads to a lock
order inversion problem, because these are called in contexts where
the vcpu mutex is held, but the vcpu mutexes nest within kvm->lock
according to Documentation/virtual/kvm/locking.txt.  Hence there
is a possibility of deadlock.

To fix this, we simply don't take the kvm->lock mutex around these
calls.  This is safe because the implementations of kvm_for_each_vcpu()
and kvm_get_vcpu_by_id() have been designed to be able to be called
locklessly.

Signed-off-by: Paul Mackerras <paulus@ozlabs.org>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

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Paul Mackerras 2019-05-23 16:36:32 +10:00

parent 1659e27d2b

commit 5a3f49364c

1 changed files with 1 additions and 8 deletions

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arch/powerpc/kvm/book3s_hv.c

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